Electrosurgical device

ABSTRACT

A surgical instrument having an end effector mounted on the end of an elongate shaft extending from a handle. The end-effector is capable of different operations, including grasping, cutting, and sealing and/or coagulating tissue, and one of the operations is controlled by a trigger mechanism contained within the handle. In some embodiments, the end effector includes a blade assembly, the trigger mechanism being arranged to drive the blade assembly longitudinally within the elongate shaft. Specifically, the trigger mechanism is formed of a three pivot slider-crank mechanism, wherein one of the pivot points includes a component to which the proximal end of the blade assembly is connected. In this respect, the proximal end of the blade assembly has a distinctive profile corresponding to the internal profile of the component such that the blade can be easily connected to the component without the need for any further features and subsequently retained therein.

TECHNICAL FIELD

Embodiments of the present invention described herein relate to anelectrosurgical device, and in particular an electrosurgical forcepsdevice wherein a mechanical blade provides a tissue cutting action incombination with electrosurgical electrodes providing a tissuecoagulation or sealing effect.

BACKGROUND TO THE INVENTION AND PRIOR ART

Electrosurgical instruments provide advantages over traditional surgicalinstruments in that they can be used for coagulation and tissue sealingpurposes. One such prior art arrangement is known from US2015/223870A1,which describes an endoscopic bipolar forceps including a housing and ashaft, the shaft having an electrosurgical end effector assembly at adistal end thereof, which includes two jaw members for grasping tissuetherebetween. Each jaw member is adapted to connect to anelectrosurgical energy source, enabling them to affect a tissue seal totissue held therebetween. A drive assembly is included within thehousing for moving the jaw members. A movable handle is also included,such that movement of the handle actuates the drive assembly to move thejaw members relative to each other. A knife channel is included withinthe end effector configured to allow reciprocation of a knife bladewithin the knife channel, to allow cutting of tissue.

Other prior art arrangements include U.S. Pat. No. 5,730,740, U.S. Pat.No. 5,104,397, U.S. Pat. No. 4,800,880, WO98/14124, US2012/0109186, U.S.Pat. No. 5,352,235, WO2014/074807, U.S. Pat. No. 7,846,161,WO2008/024911, U.S. Pat. No. 5,776,130, U.S. Pat. No. 6,039,733, U.S.Pat. No. 6,179,834, U.S. Pat. No. 7,131,971, U.S. Pat. No. 7,766,910,EP2628459, US2014/0221999, U.S. Pat. No. 7,083,618, US2009/0248020,US2015/0209103, U.S. Pat. No. 5,797,938 and U.S. Pat. No. 7,101,373.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide an improved surgicalinstrument having an end effector mounted on the end of an elongateshaft extending from a handle. The end-effector is capable of severaldifferent operations, including grasping, cutting, and sealing and/orcoagulating tissue, and one of the operations is controlled by a triggermechanism contained within the handle. In some embodiments, the endeffector includes a blade assembly, the trigger mechanism being arrangedto drive the blade assembly longitudinally within the elongate shaft inorder to cut tissue. Specifically, the trigger mechanism is formed of athree pivot slider-crank mechanism, wherein one of the pivot pointscomprises a component to which the proximal end of the blade assembly isconnected. In this respect, the proximal end of the blade assembly has adistinctive profile corresponding to the internal profile of thecomponent such that the blade can be easily connected to the componentwithout the need for any further features and subsequently retainedtherein. Such a configuration therefore provides a secure arrangementthat simplifies the assembly of the instrument.

From a first aspect, there is provided a surgical instrument including

-   -   a handle,    -   an elongate shaft extending from the handle and defining a        longitudinal axis for the instrument,    -   a blade assembly located within the elongate shaft, the blade        assembly including a cutting blade at its distal end, the blade        assembly being connected at its proximal end to a component        within the handle,    -   a trigger mechanism located on the handle and movable between a        first position and a second position, movement of the trigger        mechanism from its first position to its second position causing        the movement of the component within the handle and hence the        longitudinal movement of the cutting blade,        characterised in that the component comprises a casing having a        chamber therein, the chamber being sized to receive the proximal        end of the blade assembly, the casing including at least one        shoulder so as to provide an opening to the chamber, the opening        being of a smaller width than that of the chamber,    -   the proximal end of the blade assembly being profiled such that        it offers a first width when the blade assembly is presented to        the opening at a predetermined angle to the longitudinal axis of        the instrument, the first width being less than that of the        opening,    -   the profile of the proximal end of the blade assembly being such        that it offers a second width when the blade assembly is        presented to the opening aligned with the longitudinal axis of        the instrument, the second width being greater than that of the        opening, such that the proximal end of the blade assembly can be        inserted into the chamber when the blade assembly is presented        to the opening at the predetermined angle to the longitudinal        axis of the instrument, but the proximal end of the blade        assembly is constrained within the chamber when the blade        assembly is moved along the longitudinal axis of the instrument.

As such, the cutting blade and the internal chamber of the component areadvantageously shaped such that the blade can be easily inserted intothe component and then retained therein without the need for any furtherfeatures. Consequently, the blade is firmly secured within the componentsuch that actuation of the trigger mechanism drives the blade along theelongate shaft.

The proximal end of the blade assembly may be in the form of a bar,having a thickness substantially less than either its width or itslength.

Additionally, the proximal end of the blade assembly may include a tabat its proximal extremity, the tab extending in one direction beyond theprofile of the remainder of the proximal end of the blade assembly.

The proximal end of the blade assembly may further include a recessedportion adjacent the tab.

The proximal end of the blade assembly may further include a cut-awayopposite the tab, wherein the cut-away comprises a bevelled edge to theblade assembly.

The first width may thus be constituted by the distance between therecessed portion and the cut-away, and the second width may constitutedby the distance between the tab and the blade assembly adjacent thecut-away.

The recessed portion may be curved so as to guide the tab into thechamber as the blade assembly is rotated from the predetermined angletowards the longitudinal axis.

The shoulder may be curved to as to match the profile of the recessedportion.

The casing may comprise a two-piece assembly, a first piece defining thechamber and a second piece defining the shoulder, wherein the secondpiece is rotatably connected to the first piece.

A further aspect of the invention provides a surgical instrumentcomprising: a handle, an elongate shaft extending from the handle anddefining a longitudinal axis for the instrument, a blade assemblylocated within the elongate shaft, and a trigger mechanism located onthe handle and movable between a first position and a second position.The trigger mechanism has a component connected to the proximal end ofthe blade assembly, the arrangement of the trigger mechanism and thecomponent being such that movement of the trigger mechanism from itsfirst position to its second position causes longitudinal movement ofthe blade assembly. In addition, the component comprises an internalcavity of a first shape profile and the proximal end of the bladeassembly is of a second shape profile, the first shape profile andsecond shape profile being selected so as to permit the proximal end ofthe blade to be inserted into the internal cavity at an angle to thelongitudinal axis, and to secure the proximal end of the blade withinthe internal cavity when the blade is subsequently rotated towards thelongitudinal axis. As such, easy assembly of the blade within theinstrument is obtained.

In an embodiment the blade is rotated to rest parallel to thelongitudinal axis to lock the proximal end of the blade within thecomponent. In particular embodiments the internal cavity has asubstantially L-shaped profile, and the proximal end of the bladeassembly has a corresponding substantially L-shaped profile but withmaterial removed from inner and outer surfaces of the corner of the L asto reduce the width of the L-shaped profile at the corner thereof. Sucha shape allows the easy to use angled insertion, rotate to lock assemblymethod provided by embodiments of the invention.

From a further aspect there is therefore also provided a method ofassembling a surgical instrument having a handle, an elongate shaftextending from the handle and defining a longitudinal axis for theinstrument, a blade assembly located within the elongate shaft, and atrigger mechanism located on the handle and movable between a firstposition and a second position, the trigger mechanism having a componentconnected to the proximal end of the blade assembly to receive andretain the proximal end, the method comprising:

-   -   presenting the proximal end of the blade assembly to the        component at an angle to the longitudinal axis of the        instrument;    -   receiving the proximal end of the blade assembly within an        internal cavity of the component at the presented angle; and    -   rotating the blade assembly towards the longitudinal axis to        secure the proximal end of the blade assembly within the        internal cavity;    -   wherein the proximal end of the blade assembly and the internal        cavity of the component are of respective co-operating shapes so        as to permit the receiving of the proximal end within the        internal cavity at the presented angle and to then secure the        proximal end within the cavity at after the rotation of the        blade assembly.

With respect to the respective co-operating shapes, in one embodimentthe internal cavity has a substantially L-shaped profile, and theproximal end of the blade assembly has a corresponding substantiallyL-shaped profile but with material removed from inner and outer surfacesof the corner of the L as to reduce the width of the L-shaped profile atthe corner thereof. The reduced width profile at the corner of the Lallows the proximal end of the blade assembly to be inserted into theinternal cavity at an angle to the longitudinal axis of the instrument.In this respect, the long axis of the L shaped profile of the internalcavity is axially aligned in the same direction as the long axis of theinstrument.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be further described by way ofexample only and with reference to the accompanying drawings, whereinlike reference numerals refer to like parts, and wherein:

FIG. 1 is a side view of an electrosurgical instrument according to anembodiment of the present invention;

FIG. 2 is a side view of the handle of the electrosurgical instrumentaccording to the embodiment of the present invention;

FIG. 3 is an exploded view of an electrosurgical instrument according tothe embodiment the present invention;

FIG. 4 is a sectional view of the clamping mechanism of theelectrosurgical instrument of FIG. 3, shown in an open configuration;

FIG. 5a is a sectional view of the clamping mechanism of theelectrosurgical instrument of FIG. 3, shown in a closed configuration;

FIG. 5b is a sectional view of the clamping mechanism of theelectrosurgical instrument of FIG. 3, shown in a closed configurationwith tissue clamped therebetween;

FIG. 6 is a sectional view of part of the clamping mechanism of theelectrosurgical instrument of FIG. 3;

FIG. 7 is a perspective view of the clamping mechanism of theelectrosurgical instrument of FIG. 3;

FIGS. 8a-8f illustrate the assembly of a part of the electrosurgicalinstrument of FIG. 3;

FIGS. 9a-9b are sectional views of a part of the electrosurgicalinstrument of FIG. 3;

FIGS. 10a-10c show a blade guide part of the electrosurgical instrumentof FIG. 3;

FIG. 11 shows a latch part of the electrosurgical instrument of FIG. 3;

FIG. 12 shows a blade angle adjustment part of the electrosurgicalinstrument of FIG. 3;

FIGS. 13a-13b are sectional views of the blade angle adjustment part ofthe electrosurgical instrument of FIG. 3;

FIGS. 14a-14b show a blade angle control wheel part of theelectrosurgical instrument of FIG. 3;

FIGS. 15a-15b illustrate the rotational movement of the blade anglecontrol wheel of the electrosurgical instrument of FIG. 3;

FIGS. 16a-16d illustrate the rotational movement of the end effector ofthe electrosurgical instrument of FIG. 3;

FIG. 17 is a sectional view of the electrosurgical instrument of FIG. 3illustrating a wiring path;

FIGS. 18a-18b show further details of an electrical wiring path used inthe electrosurgical instrument of FIG. 3;

FIG. 19 shows further details of an electrical wiring path used in theelectro surgical instrument of FIG. 3;

FIGS. 20a-20b are side views of part of the cutting mechanism of theelectrosurgical instrument of FIG. 3;

FIG. 21 is a sectional view of part of the cutting mechanism of theelectrosurgical instrument of FIG. 3;

FIG. 22 is a sectional view of another part of the cutting mechanism ofthe electrosurgical instrument of FIG. 3;

FIG. 23 is a partially transparent perspective view of part of thecutting mechanism of the electrosurgical instrument of FIG. 3;

FIGS. 24a-24c illustrate the assembly of one part of the cuttingmechanism of the electrosurgical instrument of FIG. 3;

FIGS. 25a-25c are sectional views of the cutting mechanism and clampingmechanism of the electrosurgical instrument of FIG. 3;

FIGS. 26a-26f are sectional views illustrating the operation of thelatching mechanism of the electrosurgical instrument of FIG. 3;

FIG. 27 is a graph illustrating the cutting mechanism of theelectrosurgical instrument of FIG. 3;

FIGS. 28a-28b are line drawings illustrating the cutting mechanism ofthe electrosurgical instrument of FIG. 3;

FIGS. 29a-29b show a blade angle adjustment part of the electrosurgicalinstrument of FIG. 3;

FIG. 30 is a perspective view of part of the clamping mechanism of theelectrosurgical instrument of FIG. 3

FIG. 31 is a partially section view of the cutting mechanism andclamping mechanism of the electrosurgical instrument of FIG. 3;

FIG. 32 is a partially section view of the cutting mechanism andclamping mechanism of the electrosurgical instrument of FIG. 3;

FIG. 33 shows the blade angle control wheel part and the electrodecontrol switch of the electrosurgical instrument of FIG. 3;

FIG. 34 shows the blade angle control wheel part of the electrosurgicalinstrument of FIG. 3;

FIGS. 35a-35b illustrate the handle of the electrosurgical instrument ofFIG. 3, held by users with different size hands;

FIGS. 36a-36c illustrate the rotational movement of the end effector ofthe electrosurgical instrument of FIG. 3;

FIG. 37 illustrates the rotational movement of the blade angle controlwheel of the electrosurgical instrument of FIG. 3;

FIG. 38 is a schematic perspective view of an example end effector;

FIG. 39 is an enlarged perspective view of a part of the end effector ofFIG. 38;

FIG. 40 is a schematic sectional view of a part of the end effector ofFIG. 38;

FIG. 41 is a schematic perspective view of an alternative end effector;

FIG. 42 is an enlarged perspective view of a part of the end effector ofFIG. 41,

FIG. 43 is a schematic sectional view of a part of the end effector ofFIG. 41,

FIG. 44 is a schematic sectional view of a part of a further alternativeend effector;

FIG. 45 is a representation of an electro-surgical system including agenerator and an instrument in accordance with embodiments of theinvention;

FIG. 46 further illustrates a latch part of the electrosurgicalinstrument of FIG. 3; and

FIGS. 47a-47e illustrate the distal end of the cutting blade used in theelectrosurgical instrument of FIG. 3.

DESCRIPTION OF THE EMBODIMENTS

An embodiment of the invention will now be described. A brief overviewof the whole embodiment will first be given, followed by detaileddescriptions of particular aspects thereof.

1. Overview of the Configuration of the Instrument

FIG. 1 illustrates an electrosurgical instrument 1 according to anexample of the present invention. The instrument 1 includes a proximalhandle portion 10, an outer shaft 12 extending in a distal directionaway from the proximal handle portion, and a distal end effectorassembly 14 mounted on a distal end of the outer shaft. The end effectorassembly 14 may by way of example be a set of opposed jaws arranged toopen and close, and comprising one or more electrodes arranged on or asthe inner opposed surfaces of the jaws and which in use have connectionsto receive an electrosurgical radio frequency (RF) signal for thesealing or coagulation of tissue. The jaws are further provided with aslot or other opening within the inner opposed surfaces through which amechanical cutting blade or the like may protrude, when activated by theuser. In use, the handle 10 is activated by the user in a first mannerto clamp tissue between the jaws 14, and in a second manner to supplythe RF current to the electrodes in order to coagulate the tissue. Thejaws 14 may be curved so that the active elements of the instrument 1are always in view. This is important in vessel sealing devices that areused to operate on regions of the body that obscure the user's vision ofthe device during use. The handle 10 may be activated by the user in athird manner to cause the blade to protrude between the jaws 14, therebycutting the tissue clamped between. Once the required cutting andsealing has been completed, the user can release the tissue from thejaws 14.

The handle 10, as shown by FIG. 2, comprises a casing 20 formed of twoclamshell mouldings 300, 302 which houses all of the components requiredto operate and rotate the jaws 14, coagulate and cut tissue. Theclamshell mouldings in the assembled device are ultrasonically weldedtogether, once the internal components have been assembled inside. Thehandle 10 includes a clamping handle 22 for clamping tissue between thejaws 14, a trigger 24 for cutting the tissue, switch 26 for activatingand deactivating the RF supply to the electrodes in the jaws 14 in orderto coagulate tissue, and a rotation wheel 28 for rotating the jaws 14 inorder to reach tissue from different angles. As such, the configurationof handle 10 is such that the instrument 1 and all its functions can beoperated using a single hand, with all of the operational mechanismsbeing easily accessible.

FIG. 3 shows all of the features of instrument 1 required to perform itsfunctions, including those housed within the two clamshell mouldings300, 302 of the casing 20. To clamp tissue between the jaws 14, aclamping mechanism is actuated using the clamping handle 22. The clamphandle 22 further comprises a collar 304, the collar 304 comprising ahinge 306 that functions as a fulcrum around which the clamping handle22 rotates. For example, the hinge 306 may be two outward facing pinsthat click in to corresponding mouldings 308 integral to the clamshellmouldings 300, 302 to thereby provide an anchor point around which theclamping handle 22 rotates. The clamping mechanism further comprises acollar moulding 310, a spring 312, and an inner moulding 314, as furtherillustrated by FIGS. 4 to 7, all of which are threaded along a driveshaft 316.

The collar 304 comprises a keyhole aperture 318 in which the collarmoulding 310 sits. The aperture 318 has a larger diameter at the topthan that at the bottom, wherein the collar moulding 310 is arranged tosit within the lower part of the aperture 318, as illustrated by FIGS.8a . In assembly, the collar moulding 310 easily fits through the largerpart of the aperture 318 such that the collar 304 sits between twoflanges 800, 802, as shown by FIGS. 8b -8 c. As shown by FIG. 8d , thecollar 304 is then pushed upwards to engage the smaller part of thekeyhole aperture 318 with the collar moulding 310. Once, the hinge 306is connected to the hinge mouldings 308 within the casing 20, the collarmoulding 310 is retained within the lower part of the aperture 318 whereit is free to move rotationally within the aperture 318.

As shown in FIG. 6, the collar moulding 310, spring 312 and innermoulding 314 are retained between protruding members 600, 602 such thatthey cannot travel axially beyond these protruding members 600, 602. Inthis respect, the protruding members 602 at the proximal end of thedrive shaft 316 are compressible so as to allow the drive shaft 316 tobe passed through a channel 604 in the proximal end of the innermoulding 314. The drive shaft 316 is pushed through the channel 604until it reaches an opening 606, wherein the protruding members 602 areno longer compressed such that they lie flush against the walls of thedrive shaft 316. Instead, the protruding members 602 fan out and pushagainst the walls of the opening 606 such that the span of theprotruding members 602 extends beyond the diameter of the channel 604.Consequently, the drive shaft 316 cannot be pulled back through thechannel 604 and is thus locked in place.

The distance between the protruding members 600, 602 is such that thespring 312 is at least partially compressed between the collar moulding310 and the inner moulding 314. This pre-compression is important forensuring that the correct clamping load is applied when the clampingmechanism is activated, as will be described in more detail below. Boththe collar moulding 310 and the inner moulding 314 comprise cavities608, 610 into which the spring 312 extends. In particular, a substantialproportion of the length of the collar moulding 310 houses the spring312. This arrangement allows for a longer spring 312 which is importantfor ensuring that the spring 312 does not ever reach its solid lengthduring use.

The main body of the drive shaft 316 lies within the outer shaft 12, thedistal end of the drive shaft 316 being coupled to both the distal endof the outer shaft 12 and the jaws 14. The drive shaft 316 moves axiallywithin the outer shaft 12 and it is this axial movement that moves thejaws 14 from an open to a closed position, as can be seen from FIGS. 4and 5 a. For example, the drive shaft 316 is coupled to the jaws 14 bymeans of a drive pin 400 in a cam slot 402, whereby movement of thedrive pin 400 within the cam slot 402 moves the jaws 14 between the openand closed position. The coupling between the drive shaft 316, the outershaft 12 and the jaws 14 is such that rotational movement of the driveshaft 316 is transferred to the outer shaft 12 and jaws 14.

The outer shaft 12 and drive shaft 316 are coupled at a further point bymeans of a shaft moulding 320. The shaft moulding 320 sits within asocket 322 of the casing 20, and thus couples the outer shaft 12 to thecasing 20. The outer shaft 12 is attached to the shaft moulding 320 byany suitable means, for example, snap-fit tabs 900 that cooperate withcorresponding notches 902 within the shaft moulding 320, as shown inFIG. 9b . The drive shaft 316 is threaded through the body of the shaftmoulding 320 via an aperture (not shown) that matches thecross-sectional “T” shape of the drive shaft 316, as illustrated by FIG.10a . The shaft moulding 320 is arranged such that it is free to rotatewithin the socket 322. For example, the shaft moulding 320 may comprisecylindrical flange features 904, 906 that rotate within concentricmating faces 908, 910 provided within the clamshell mouldings 300, 302.Therefore, the shaft moulding 320 rotates with the drive shaft 316,which in turn translates this rotational movement to the outer shaft 12and the jaws 4. The shaft moulding 320 thus acts as a rotational andaxial guide for the drive shaft 316.

The clamping handle 22 comprises a latch 324 arranged to cooperate witha latch moulding 326 which sits within the proximal end 328 of thecasing 20. The latch moulding 326 may be held in place by any suitablemeans, for example, by means of a moulded pin 330 integral to one of theclamshell mouldings 300, 302, as shown by FIG. 3, or by simply by themoulded walls 1100 integral to the clamshell moulding 300, as shown byFIG. 11. When the clamping handle 22 is driven towards the casing 20 soas to close the jaws 14, the latch 324 enters the casing 20 via anopening 1102 and engages with the latch moulding 326 so as to retain theclamping handle 22 in this position. As is shown in FIGS. 26a to 26f ,the latch moulding 326 comprises a two way spring 1104 and a cam path1106 along which the latch 324 traverses. As shown in FIG. 46, the latchmechanism may also include an override component 4600 to allow the userto manually release the latch 324 if it gets stuck, and a lock-outcomponent 4602 to disable the latch mechanism altogether. The overridecomponent 4600 and lock-out component 4602 may be provided on the latchmoulding 326 or may be integral to the inside of the casing 20.

As described above, the handle 10 further comprises a rotation wheel 28,wherein the rotation wheel 28 is arranged to encase the inner moulding314. In this respect, the rotation wheel 28 and inner moulding 314 haveinterlocking members 1200, 1202, as shown by FIG. 12. These interlockingmembers 1200, 1202 couple together such that the rotation wheel 28 andinner moulding 314 rotate together, whilst still allowing axial movementof the inner moulding 314 within the rotation wheel 28, as can be seenfrom FIGS. 13a -13 b. Therefore, rotation of the rotation wheel 28causes rotation of the inner moulding 314, which subsequently rotatesthe drive shaft 316 and the collar moulding 310. For stability, therotation wheel 28 comprises cylindrical faces 1204 that rotationallyslide on internal mating faces (not shown) integral to the clamshellmouldings 300, 302.

To enable the user to rotate the jaws 14, the casing 20 has two openings332, 334 through which scalloped portions 336 of the rotation wheel 28protrude. The two openings 332, 334 are opposite one another on eachside of the handle, and are trapezoidal in shape. In particular, thetrapezoidal apertures have parallel sides orthogonal to the longitudinalaxis of the handle, and one of the parallel sides may be longer than theother, the longer side being at the forward end of the aperture, and theshorter side being at the rearward end. The scalloped portions 336 areconveniently sloped so as to comfortably fit the thumb or fingers of theuser. In this respect, the scalloped portions 336 are cut at an angle tothe plane of rotation, as shown in FIGS. 14a -14 b. In particular, theangle of the sloping part of the scalloped portions should besubstantially equal to the angle of the external casing in the region ofthe rotation wheel 28.

The rotation wheel 28 also comprises at least one stop member 1500 forlimiting the degree of rotation, as illustrated in FIGS. 5a -5 b. Thestop member 1500 interacts with stop features 1502, 1504 integral to thecasing 20. As the rotation wheel 28 is rotated, the stop member 1500 isobstructed by the stop features 1502, 1504, thereby preventing furtherrotation. For example, the stop features 1502, 1504 may limit therotation wheel to 270° of rotation. Similarly, the shaft moulding 320also comprises a stop member 1600 that interacts with stop features1602, 1604 integral to the casing 20, as shown by FIGS. 16a -16 d. Thestop member 1600 of the shaft moulding 320 and its respective stopfeature 1602, 1604 are radially aligned with the stop member 1500 of therotation wheel 28 and its respective stop features 1502, 1504 such thatrotation is limited to the same extent. That is, as the rotation wheel28 is turned, the radial point at which stop member 1500 on the rotationwheel 28 is obstructed will be the same as the radial point at whichstop member 1600 on the shaft moulding 320 will be obstructed. Forexample, in FIGS. 15b and 16a , the jaws 14 have been rotated 90°anticlockwise from a neutral orientation (shown in FIG. 16b ). Thisrotational freedom means that the user can grasp at tissue fromdifferent angles without needing to rotate the whole instrument 1.

As described above, the switch button 26 is provided for activating andde-activating the RF signal delivered to the electrodes in the jaws 14via some appropriate circuitry, for example, two ingress-protectedswitches on a small printed circuit board (PCB) 338. As shown in FIG.17, the PCB 338 is connected to a connection cord 1700 for receiving theRF output from a generator (not shown) and electrical wiring 1702, 1704for supplying the RF current to the electrodes in the jaws 14, forexample, one wire for the active electrode and one for the returnelectrode. As shown in FIG. 17 and FIGS. 18a-18b the wires 1702, 1704are wrapped underneath and around the shaft moulding 320 before enteringa guide slot 1800 into the internal cavity 1802 of the shaft moulding320 and down the outer shaft 12. Wrapping the wires 1702, 1704 aroundthe shaft moulding 320 in this way keeps the wires 1702, 1704 in acompact arrangement, so as to enable easy assembly, whilst allowing forthe rotation of the drive shaft 316. In this respect, the wires 1702,1704 un-wind and re-wind with the rotation of the drive shaft 316.Additionally, one of the clamshell mouldings 300 also comprises twomoulded pockets 1900, 1902 located in series for housing the wirecontacts 1904, 1906 that connect the active and return wires 1702, 1704to the wiring 1908, 1910 of the ingress-protected switches 338. Theopposite clamshell moulding 302 comprises corresponding rib features(not shown) to retain the contacts 1904, 1906 within the pockets 1900,1902. As a result, the two wire contacts 1904, 1906 are longitudinallyseparated such that only one contact can pass through each pocket 1900,1902, thereby providing a physical barrier between each contact 1904,1906 and any wiring. This prevents the risk of insulation damage to anyof the wiring caused by the contacts 1904, 1906, whilst also protectingthe contacts 1904, 1906 themselves from any fluid that may make its waydown the outer shaft 12 and into the casing 20.

Turning to the cutting mechanism, a blade 340 for cutting tissue clampedbetween the jaws 14 is provided within a central track 342 along thelength of the drive shaft 316. The mechanism for actuating the blade 340along the track 342 and between the jaws 14, is operated via the trigger24. The trigger 24 actuates a drive assembly formed of a triggermoulding 344, a blade drive moulding 346, a blade collar moulding 348,an extension spring 350 and a blade moulding 352. The drive assembly ispositioned between the shaft moulding 320 and the handle collar 304 ofthe clamping mechanism. As shown in FIGS. 20a -20 b, the drive assemblyfunctions as an offset slider-crank mechanism whereby the force exertedby the user on the trigger 24 is transferred into axial movement of theblade moulding 352 along the drive shaft 316, which in turn drives theattached blade 340.

As shown in FIGS. 21, 22 and 23, the blade moulding 352 is arranged tosit within the blade collar moulding 348. As shown in FIG. 22, the bladecollar moulding 348 comprises a lip 2200 the interlocks with a groove2202 around the circumference of the blade moulding 352. As shown onFIG. 23, the blade moulding 352 has a “T” shaped aperture 2300 forreceiving the drive shaft 316 and blade 340. The blade moulding 352further comprises an internal cut-out 2100, as shown by FIG. 21, for theproximal end of the blade 340, wherein the end of the blade 2102 isshaped to match the internal cut-out 2100 of the blade moulding 352 soas to allow ease of assembly, as demonstrated by FIGS. 24a-24c . Theblade moulding 352 is isolated rotationally from the blade collarmoulding 348 such that the two mouldings can rotate concentrically.Consequently, the blade moulding 352 is able to rotate with the driveshaft 316.

As described above, the jaws 14 may be curved. To enable the blade 340to be pushed around the curve, whilst maintaining sufficient cuttingability, the frictional force of the cutting blade 340 through thecurved track must be minimised. The frictional force is a product of thefrictional coefficient of the blade 340 within the track 342, and theforce due to bending that the blade 340 exerts on the walls of the track342. This frictional force may be reduced, for example, by adding a lowfriction coating to the sides of the blade, and/or preferentiallyweakening the blade 340 to graduate the flexibility of the blade'sdistal end such that it is able to bend along the track 342 whilstremaining rigid in the direction of the cutting force. Preferentialweakening may be provided, for example, by the provision of one or moreapertures 354 in the distal end, as shown in FIG. 3 and FIGS. 47a -47 c,or by graduating the blade 340 thickness, as illustrated in FIG. 47d .Alternatively, as illustrated by FIG. 47e , patterned laser cuts 4712 orchemical etches in the distal end could be used to control the bendingstiffness over a length of the blade, whereby the spacing between suchcuts may be constant or gradually increase from the distal to proximalend.

In use, blood and tissue can build up within the distal end of theinstrument 1. In particular, blood and tissue can cause the blade 340 tostick within the drive shaft 316. Therefore, the distal end of the driveshaft 316 may include cut-out portions 1000, 1002 in order to reduce thesurface area of the drive shaft 316 to which blood and tissue buildstick, as shown in FIGS. 10b -10 c. For example, the cut-out portionsmay be such that the distal end comprises two side walls with no basesupport, or the distal end comprises a base support with bifurcated sidewalls.

2. Operation of the Instrument

Having described the overall configuration of the device, the overalloperation of the electrosurgical instrument 1 in use will now bediscussed. Following this, further detailed description of theconfiguration and operation of particular aspects of the device will beundertaken.

As discussed above, the handle 10 of the electrosurgical instrument isarranged to i) clamp tissue between a set of jaws 14, ii) latch the jawsin place (if desired by the user), iii) deliver an RF signal toelectrodes in the jaws 14 so as to coagulate the tissue clamped between,and iv) launch a blade 340 between the jaws 14 so as to cut the tissueclamped between. The handle 10 can also rotate the jaws 14 so as toallow the user to clamp tissue at different angles without needing torotate the entire handle 10. The result is that the tissue between thejaws can be sealed prior to or at the same time as being cut by the sameelectrosurgical instrument. Moreover, these effects can be achieved bythe instrument via a one handed operation thereof by the surgeon.

2.1 Clamping Mechanism

To clamp tissue between the jaws 14, the user squeezes the clampinghandle 22 towards the proximal end 328 of the casing 20 until the latch324 engages with the latch moulding 326 within the casing 20. Thismovement pivots the drive handle 22 about its hinge 306, as shown byFIGS. 8e -8 f, and pushes the edge of the collar 304 against the flange800 to drive the collar moulding 310, the spring and the inner moulding314 along the drive shaft 316 in the proximal direction, as illustratedby FIGS. 4 and 5 a. As described above, the inner moulding 314 isattached to the drive shaft 316 via protruding members 602. Therefore,as the inner moulding 314 is pushed back axially, the drive shaft 316 isalso moved axially which drives the pin 400 in the cam slot 402 of thejaws 14, thereby closing the jaws 14. As such, the load from the drivehandle 22 is transferred to the drive shaft 316 via the spring mechanismof the collar moulding 310, spring 312 and inner moulding 314.

Once tissue is clamped between the jaws 14, as shown by FIG. 5b , thespring 312 acts to limit the force loaded onto the tissue. Once thecollar moulding 310, spring 312 and inner moulding 314 have stoppedmoving axially, and as the collar 304 continues to drive against theflange 800, the threshold compression force on the spring 312 iseventually reached such that the spring 312 begins to compress betweenthe collar moulding 310 and inner moulding 314. As the spring 312compresses further, the drive handle 22 can be driven all the way intothe latched position without exerting any more force on the clampedtissue. That is, the load of the drive handle 22 is no longertransferred to the drive shaft 316, but is effectively absorbed by thespring 312. As such, the spring 312 ensures that the correct amount ofload is transferred onto the jaws 14. Without the spring 312, actuationof the drive handle 22 will continue to increase the load transferred tothe drive shaft 316 and subsequently the jaws 14 and tissue. This couldresult in mechanical damage to the tissue as the user continues tosqueeze the drive handle 22 in order to engage the latch 324.

As discussed above, the cavities 608, 610 in the collar moulding 310 andinner moulding 314 act together to allow for a larger spring 312. Thisallows for greater spring travel so that the spring 312 does notcompletely compress to its solid length during use. If the spring 312was to reach its solid length, the spring would no longer absorb theload exerted by the drive handle 22 and the force would once again betransferred to the jaws 14.

2.2 Latch Mechanism

Once tissue has been clamped between the jaws 14, the jaws 14 can belocked into a closed position by engaging the latch 324 on the drivehandle with the latch moulding 326 inside the casing 20 as shown byFIGS. 26a -26 f. As the latch 324 enters the casing 20 via the opening1102, the latch 324 engages the latch moulding 326, pushing the moulding326 down within the casing 20 and thereby extending the spring 1104. Asshown in FIGS. 26b -26 c, the latch 324 runs up the side of the cam path1106 until it reaches its maximum position. At this point, the drivehandle 22 cannot be compressed any further, and the spring 1104 pullsthe latch moulding 326 back up inside the casing 20 such that the latch324 slots into the “V” shaped pocket of the cam path 1106 to retain thedrive handle 22 in the compressed position and the jaws 14 in the closedposition, as shown in FIG. 26 d.

In this latched position, the user's hand is free for operating theother functions of the instrument 1, as will be discussed below.

To release the latch 324 from the casing 20 and open the jaws 14, theuser must squeeze drive handle 22 towards the casing 20 to release thelatch 324 from the pocket of the cam path 1106, as shown by FIG. 26e .The force of the spring 1104 pulls the latch moulding 326 further upinto the casing 20, such that the latch 324 travels in the oppositedirection down the side of the cam path 1106, as shown by FIGS. 26e -26f, and back out of the opening 1102. The latch moulding 326 will thenreturn back to its original position within the casing 20.

2.3 Cutting Mechanism

Whilst the jaws 14 are in a closed position, the user may need to cutthe tissue clamped between. To cut the tissue, a blade 340 is drivenbetween the jaws 14 by actuation of the drive assembly.

The drive assembly is a three pivot arrangement that acts as aslider-crank mechanism. As the user pulls the trigger 24 back towardsthe casing 20, as shown by FIGS. 25b -25 c, it levers the triggermoulding 344 around a pivot point A which is anchored to the casing 20,for example, by means of outward facing pins 358 that connect withcorresponding mouldings 356 integral to the clamshell mouldings 300, 302shown in FIG. 3. This urges the pivot point B connecting the triggermoulding 344 and drive moulding 346 over its centre position, therebydriving the blade collar 348, blade moulding 352 and blade 340 along thedrive shaft 316 at a force sufficiently high that the blade 340 is ableto cut the clamped tissue. In this respect, the load exerted on thetrigger 24 is transferred to the blade collar 348 and blade moulding 352via the trigger moulding 344 and drive moulding 346. As the pivot pointB moves over centre into its protracted position, the speed at which theblade collar 348 and blade moulding 352 are driven along the drive shaft316 accelerates, thus increasing the force of the blade 340. As such,the force at which the blade 340 cuts into the tissue increases withoutthe user exerting any additional force on the trigger 24.

The shaft moulding 320 acts as a stopping point for the blade collar 348and blade moulding 352. Consequently, the pivot point B always remainsabove the two other pivot points A, C with respect to the drive shaft316.

During actuation of the trigger 24, the force exerted on the trigger 24is big enough to overcome the compression force of the extension spring350 such that it extends along the same plane as the drive shaft 316 toallow for the axial movement of the blade collar 348 and blade moulding352. On release of the trigger 24, the extension spring 350re-compresses to retract the drive assembly to its original position. Inthis respect, the tension of the extension spring 350 is strong enoughto retract the blade 340 through thick tissue without the need for userintervention.

2.4 Shaft Rotation

During use, the user may need to reach tissue from different angleswithout needing to move the entire instrument 1. Therefore, the jaws 14are advantageously rotatable relative to the handle 10 by means of therotation wheel 28. This is particularly beneficial where the jaws 14 areon a curved track, such as those shown in FIGS. 16a -d. As describedabove, the rotation wheel 28 is coupled to the inner moulding 314 viainterlocking members 1200, 1202 such that the inner moulding 314 rotateswith the rotation wheel 28. As the end of the drive shaft 316 isconnected to the inner moulding 314, the drive shaft 316 also rotateswhich subsequently rotates the jaws 14 at its opposite end.

To facilitate this rotational movement without interfering with theoperation of the clamping mechanism, the collar moulding 310 isrotationally isolated within the handle collar 304 such that the collarmoulding 310 also rotates with the drive shaft 316. Likewise, so as toallow drive shaft 316 rotation without interfering with the operation ofthe cutting mechanism, the blade moulding 352 is rotationally isolatedwithin the blade collar 348.

In order to transfer the rotational movement to the outer shaft 12, theshaft moulding 320 is rotationally isolated within its socket 322. Asdescribed above, the shaft moulding 320 acts as a rotational guide so asto control the rotational movement relative to the shaft 316 along theentire length of the instrument 1. Additionally, the active and returnwires 1702, 1704 are arranged within the casing 20 so as to preventdamage to these wires 1702, 1704 as a result of the rotating components.As described above, the wires 1702, 1704 are wrapped around the shaftmoulding 320 so as to allow for the degree of rotation of the driveshaft 316. Consequently, the wires 1702, 1704 un-wind and re-wind aroundthe shaft moulding 320 as it rotates.

2.5 Electrode Activation

Whilst the jaws 14 are in a closed position, the user may wish tocoagulate and seal the tissue clamped between. To do this, the userinitiates electrode activation using the switch button 26 on the top ofthe casing 20, positioned conveniently so that the user can easilyaccess the button 26 whilst using the device single handed. In doingthis, an appropriate RF signal is delivered to the electrodes in thejaws 14 so as to coagulate and seal the tissue. The RF signal may be apure or blended waveform, depending on the desired effect.

Having given an overview of the configuration and operation of thedevice as a whole, further detailed description of the configuration andoperation of particular aspects thereof will now be given.

3. Clamping Mechanism Assembly and Operation

As described above, the proximal handle portion 10 of theelectrosurgical instrument 1 includes a first mechanism for actuatingone aspect of a distal end effector assembly 14 such that the endeffector assembly 14 moves between a first and second condition. Forexample, the end effector assembly 14 may be a set of opposed jaws 14arranged to open and close. The mechanism used to trigger movement ofthese jaws 14 is the so called clamping mechanism comprising a drivehandle 22 and two barrel shaped mouldings 310, 314 with a spring 312compressed therebetween, all of which are threaded along an elongate bar316 that extends between the jaws 14 and the handle 10, as shown inFIGS. 4 and 5 a-5 b.

As shown in FIG. 8a , the drive handle 22 comprises a collar 304 inwhich the collar moulding 310 sits. The collar 304 comprises an aperture318 shaped like a keyhole or a figure of eight. As such, the aperture318 is formed of two contiguous apertures 804, 806, wherein the topaperture 804 has a larger diameter across it than the bottom aperture806.

The collar moulding 310 is a cylindrical or barrel shaped componenthaving two flange portions 800, 802 spaced apart longitudinally. Thediameter of the proximal flange 800 is larger than both the upper andthe lower apertures 804, 806. The diameter of the distal flange 802 issmaller than the upper aperture 804 and larger than the lower aperture806.

During assembly, the collar moulding 310 is first inserted through theupper aperture 804, as shown by FIGS. 8b -8 c. As the distal flange 802is smaller than the upper aperture 804, it easily passes through,whereas the proximal flange 800 may be large enough to prevent thecollar moulding 310 from advancing the entire way through the upperaperture 804. As shown by FIG. 8d , the collar 304 is then pushedupwards to engage the lower aperture 806 with the collar moulding 310.

Once assembled, the collar moulding 310 remains within the loweraperture 806 of the collar 304 and is positioned such that its twoflanges 800, 802 lie either side of the collar 304, as shown in FIG. 8e. As lower aperture 806 has a smaller diameter than both flanges 800,802, the collar moulding 310 cannot be removed by simply pushing thecollar moulding 310 through the lower aperture 806. In contrast, thebody of the collar moulding 310 between the two flanges 800, 802 has aslightly smaller diameter than the lower aperture 806. Therefore, thecollar moulding 310 sits within the lower aperture 808 loosely enough toallow rotational movement.

As can be seen from FIG. 8e , the longitudinal distance between the twoflanges 800, 802 is only slightly larger than the thickness of thecollar 304 such that the collar 304 sits snugly between the flanges 800,802. This ensures that movement of the drive handle 22 is transferreddirectly to the collar moulding 310 and subsequently to the othercomponents of the clamping mechanism. This is particularly important forensuring that the jaws 14 are responsive to the movement of the drivehandle 22 and that there is not a delayed response between actuation ofthe drive handle 22 and movement of the jaws 14.

Once the collar moulding 310 and drive handle 22 have been assembled,the remaining components can be assembled.

The drive shaft 316 is an elongated bar with one or more protrudingmembers 602 located at its proximal end, as shown in FIG. 6. Theprotruding members 602 are flexible tabs that fan out from the surfaceof the drive shaft 316. That is to say, the protruding members 602 aredeformable such that they may be pressed flush against the surface ofthe drive shaft 316, but will return to their original positions uponrelease of any resistive force. This allows the drive shaft 316 to beeasily threaded through all of the components of the clamping mechanismduring assembly, as will now be described.

The collar moulding 310 has an internal cavity divided into two parts.The first part is a narrow channel or slot 607 for receiving the driveshaft 316, wherein the distal end of the collar moulding 310 comprisesan opening 311, as shown in FIG. 3, which matches the cross-sectional“T” shape of the drive shaft 316. The diameter of the channel 607 isonly slightly wider than that of the drive shaft 316 so as to provide asnug fit for stability. On insertion of the drive shaft 316, theprotruding members 602 are pressed flat to allow the drive shaft to bepushed all the way through.

The second part is a chamber 608 large enough to house one end of thespring 312. The chamber 608 can extend over any suitable proportion ofthe length of the collar moulding 310. For example, the length of thechamber 608 may be around 25% of the length of the collar moulding 310,or as much as 75% of the length of the collar moulding 310.

The chamber 608 is substantially larger than the collar moulding channel607 such that as the drive shaft 316 is pushed through the collarmoulding 310, the protruding members 602 span back out to their originalconfiguration when they reach the chamber 608.

The collar moulding 310 and drive handle 22 assembly is threaded downalong the drive shaft 316 until the collar moulding 310 reaches a secondset of protruding members 600. These protruding members 600 have a spanwider than the opening 311 on the collar moulding 310 so as to providean obstruction that prevents the collar moulding 310 from advancingfurther along the drive shaft 316. As such, the protruding members 600must be sufficiently rigid that the collar moulding 310 cannot be pushedpassed the protruding members 600 by exerting some force or pressing theprotruding members 600 inwards.

The drive shaft 316 is then threaded through the centre of the spring312. Preferably, the spring 312 has a diameter that is only slightlylarger than that of the drive shaft 312 to provide a close fit betweenthe spring 312 and the drive shaft 316. The spring 312 is then pushedalong the drive shaft 316 until the end of the spring 312 fills thecollar moulding chamber 608.

The inner moulding 314 is a cylindrical or barrel shaped componenthaving an internal cavity divided into two sections. The first sectionis a chamber 610 in which one end of the spring 312 is housed such thatthe spring 312 is partially encased by the collar moulding 310 and innermoulding 314. The second section is a narrow channel or slot 603 forreceiving the proximal end of the drive shaft 316. The channel 603 isdivided into two parts 604, 606. The first part of the channel 604 isshaped so as to allow the drive shaft 316 to be passed through, theflexible tabs 602 being pressed flat in doing so. As such, the diameterof the first channel part 604 is only slightly wider than that of thedrive shaft 316 so as to provide a snug fit. The snug fit of the driveshaft 316 within both the collar moulding channel 607 and inner mouldingchannel 603 means that the drive shaft 316 is held firmly in place. Thisadds to the stability of the drive shaft 316 within the casing 20, whichis particularly important for ensuring maximum control of the endeffector 14.

The second part of the channel 606 provides a shoulder 605 into whichthe protruding members 602 can extend. Consequently, as the drive shaft316 passes through the channel 604 and into the second channel part 606,the flattened protruding members 602 fan back out to their originaldecompressed positions. Once the protruding members 602 have engagedwith the shoulder 605 of the second channel part 606, the drive shaft316 cannot be pulled back through the first channel part 604 and is thusretained in the inner moulding 314. As such, the diameter of the secondchannel part 606 must be sufficiently wide that the protruding members602 are able to expand beyond the diameter of the first channel part604. To achieve this snap-fit connection, a protruding member 602 isonly required on one side of the drive shaft 316.

This snap-fit connection is such that any axial movement of the innermoulding 314 will be transferred to the drive shaft 316. Similarly, anyrotational movement of the inner moulding 314, for example, by means ofthe rotation wheel 28 formed around the inner moulding 314, is alsotransferred to the drive shaft 316.

Therefore, to complete the assembly of the clamping mechanism, the driveshaft 316 is simply threaded through the collar moulding 310, the spring312 and finally the inner moulding 314, until the protruding members 602snap into the second channel part 606.

Once assembled along the drive shaft 316, the collar moulding 310, thespring 312 and the inner moulding 314 are arranged such that the spring312 is partially encased by the collar moulding 310 and inner moulding314. By providing the collar moulding chamber 608 and inner mouldingchamber 610 in which a substantial portion of the spring 312 can behoused, a longer spring 312 can be used without using up any additionalspace within the handle 10. As such, the larger the collar mouldingchamber 608 and inner moulding chamber 610, the longer the spring 312.Furthermore, the distance between the protruding members 600, 602 meansthat the ends of the spring 312 are compressed by the end walls 612, 614of the collar moulding chamber 608 and inner moulding chamber 610respectively so that the spring 312 experiences an initialpre-compression upon installation. This is important for ensuring thatwhen the handle 22 is actuated so as to activate the clamping mechanism,the correct load is applied to the jaws 14.

Additionally, the inner moulding 314 may be contained within a furtherbarrel shaped moulding such as the rotation wheel 28 shown in FIGS. 13a-13 b. Here, the inner moulding 314 rotates with the rotation wheel 28,but is free to move axially within the internal cavity 1300 of therotation wheel 28, moving between a first position as shown in FIG. 13aand a second position as shown in FIG. 13b . Consequently, rotation ofthe wheel 28 rotates the inner moulding 314, which in turn rotates thedrive shaft 316 and the jaws 14.

Once all of the components have been assembled, the drive handle 22 canbe installed inside the casing 20. In this respect, the drive handle 22is connected to the casing at its hinge 306. For example, the hinge 306may be two outwardly extending pins that mate with corresponding hingemouldings 308 integral to the clamshell mouldings 300, 302. Thisprovides an anchor point around which the drive handle 22 can rotate.

Therefore, the above arrangement provides a mechanism for actuating theend effector assembly 14 which can be assembled easily and securelywithout the need for any additional components.

In use, the user squeezes the drive handle 22 towards the proximal end328 of the casing 20, thereby rotating the drive handle 22 about itshinge 306. In doing this, the collar 304 pushes against the proximalflange 800, thus moving the collar moulding 310 longitudinally. Thislongitudinal movement drives the spring 312, inner moulding 314 and thedrive shaft 316 back towards the proximal end of the handle portion 10,as shown by FIG. 5a . As the drive shaft 316 is coupled to the jaws 14,for example, by means of a pin 400 and cam slot 402 arrangement, thejaws 14 are moved from the open to the closed position. As such, theload from the drive handle 22 is transferred to the drive shaft 316 viathe spring mechanism of the collar moulding 310, spring 312 and innermoulding 314. This spring mechanism is particularly important as it actsto limit the force loaded onto any tissue that is clamped between thejaws 14.

As the drive handle 22 is squeezed, the collar moulding 310, spring 312and inner moulding 314 continue to move axially until either the innermoulding 314 reaches its furthest proximal position such that the jaws14 are fully closed, as shown in FIG. 5a , or the jaws 14 are unable toclose any further due to tissue 500 clamped between, as shown by FIG. 5b, in which case the drive handle 22 has not been fully actuated suchthat it is held in place by the latch 324. As the user continues tosqueeze the drive handle 22 and the collar 304 continues to driveagainst the flange 800, the threshold compression force on the spring312 is eventually reached such that the spring 312 begins to compressbetween the collar moulding 310 and inner moulding 314, as can be seenin FIG. 5 b.

As the spring 312 compresses further, the drive handle 22 can be drivenall the way into the latched position without exerting any more force onthe clamped tissue 500. That is, the load of the drive handle 22 is nolonger transferred to the drive shaft 316, but is effectively absorbedby the spring 312. As such, the spring 312 ensures that the correctamount of load is transferred onto the jaws 14. Without the spring 312,actuation of the drive handle 22 will continue to increase the loadtransferred to the drive shaft 316 and subsequently the jaws 14 andtissue 500. This could result in mechanical damage to the tissue 500 asthe user continues to squeeze the drive handle 22 in order to engage thelatch 324.

Therefore, the pre-compression of the spring 312 is important forensuring that the spring 312 bears the load of the handle 22 as soon asthe inner moulding 314 reaches its axial limit. Similarly, having alonger spring 312 allows for greater spring travel so that the spring312 does not completely compress to its solid length during use. If thespring 312 was to reach its solid length, the spring 312 would no longerabsorb the load exerted by the drive handle 22 and the force would onceagain be transferred to the jaws 14.

To retain the jaws 14 in the closed position, the latch 324 on the drivehandle 22 must be engaged with the latch moulding 326 inside theproximal end 328 of the casing 20, as shown in FIGS. 26a -26 f.

As shown in FIG. 11, the latch moulding 326 is a single integrallymoulded component comprising a body portion 1108, a spring element 1104and a cam path 1106. The proximal end 328 of the casing 20 has parallelwalls 1100 that define a channel 1110 in which the body portion 1108sits. The width of the channel 1110 is such that the body portion 1108is retained within the channel 1110 but is still able to slide up anddown the channel 1110 during use, as will be described below. In thisrespect, the latch moulding 326 is preferably made of a low frictionmaterial, for example, polytetrafluoroethylene (PTFE), to allow the bodyportion 1108 to easily slide within the channel 1110 without sticking.For further stability within the channel 1112, a moulded pin 330 may beprovided in the casing 20 which engages with a cam slot 331 provided onthe body portion 1108, as shown in FIG. 46.

The spring 1104 is located at the end of the body portion 1108 and isarranged to bias the body portion 1108 up the channel 1110 towards thedistal end of the casing 20. The spring 1104 can be of any suitableconfiguration, for example, the spring 1104 may be an arcuate or loopshape such as that shown in FIG. 11. The cam path 1106 is a mouldedprojection formed on the body portion 1108. The cam path 1106 comprisesa first cam surface 1112, a notch 1114 and a second cam surface 1116 toform a “V” shaped moulding.

The latch 324 is formed of an arm 1118 extending from the bottom of thedrive handle 22. The arm 1118 has a pin 1120 located at its end which issuitable for traversing the cam path 1106.

In use, the latch 324 enters the casing 20 via an opening 1102. The pin1120 engages the latch moulding 326 such that the body portion 1108 ispulled down channel 1110 and the spring 1104 thereby being extended. Asshown in FIGS. 26b -26 c, the pin 1120 runs up the side of the first camsurface 1112 until it reaches the top of the “V”. At this point, thedrive handle 22 cannot be compressed any further, and the spring 1104pulls the body portion 1108 back up the channel 1110 such that the pin1110 slots into the notch 1114, thus retaining the drive handle 22 inthe compressed position and the jaws 14 in the closed position, as shownin FIG. 26 d.

Therefore, to latch the drive handle 22, all the user has to do is toactuate the drive handle into the fully compressed position, wait forthe pin 1110 to click into the notch 114 and then release the drivehandle 22. In this latched position, the user's hand is free foroperating other functions of the instrument 1, such as operating thecutting mechanism using the trigger 24, rotating the jaws 14 using therotation wheel 28 or operating the electrodes in the jaws 14 using theswitch 26.

To release the latch 324 from the casing 20 and open the jaws 14, theuser must squeeze drive handle 22 towards the casing 20 once more. Thisreleases the pin 1120 from the notch 1114, as shown by FIG. 26e . As thepin 1120 exits the notch 1114, the force of the extended spring 1104pulls the body portion 1108 back up the channel 1110, such that the pin1120 runs down the side of the second cam surface 1116, as shown byFIGS. 26e -26 f. As the pin 1120 reaches the bottom of the second camsurface 1116, it pushes the body portion 1108 further up the channel1110 so that the pin 1120 can pass back out of the opening 1102. Thebody portion 1108 will then return back to its original position withinthe channel 1110.

Therefore, to release the drive handle 22, all the user has to do issqueeze the drive handle 22 towards the proximal end of the casing 20and then allow the drive handle 22 to return to its original openposition.

Additionally, the latch moulding 324 may include an override button 4600integrally formed on the body portion 1108 as shown in FIG. 46, whereinthe override button 4600 is engaged so as to alter the position of thecam path 1106 such that the pin 1120 automatically disengages with thenotch 1114 and releases the drive handle 22. Consequently, if the latchmechanism was to fail for any reason, the user would be able to releasethe drive handle 22 to open the jaws 14.

The body portion 1108 may also be provided with an integrated lock-outbar 4602 to allow the user to disengage the latch mechanism altogether,wherein the lock-out bar 4602 is moveable between a first and secondposition to manually slide the body portion 1108 within the channel1110. When the lock-out bar 4602 is in the first position, the bodyportion 1108 is in its normal position such that the latch mechanismoperates as described above. The user may then move the lock-out bar4602 to its second position, whereby the body portion 1108 is moved upthe channel 1110 such that the pin 1120 can only traverse along thesecond cam surface 1116 and is thus prevented from engaging with thenotch 1114.

It will be appreciated that such a latch mechanism may also be suitablefor many end effector assemblies. For example, such a latch may beprovided on the trigger 24 for the cutting mechanism so as to retain thecutting blade 340 in the actuated position.

On release of the latch 324, the drive handle 22 can be moved back toits original position. In doing this, the collar 304 releases the loadexerted on the proximal flange 800 and pushes against the distal flange802, thus pulling the collar moulding 310 back to its original axialposition. Consequently, the spring 312, the inner moulding 314 and thedrive shaft 316 are also pulled back axially, which in turn moves thejaws 14 back to the open configuration.

4. Cutting Mechanism Assembly and Operation

Various further features and aspects relating to the structure andoperation of the cutting mechanism will now be described. As describedabove, the proximal handle portion 10 of the electrosurgical instrument1 includes a second mechanism for actuating a further aspect of a distalend effector assembly 14. For example, the end effector assembly 14 maybe a set of opposed jaws 14 and a blade 340, wherein the distal end ofthe blade 340 is arranged to slide between the jaws 14 in order to cuttissue clamped between said jaws 14. The mechanism used to triggermovement of the blade 340, which is disposed within a central track 341of the drive shaft 316, is the so called cutting mechanism. The cuttingmechanism comprises a drive arm 2000, a blade drive moulding 346, ablade collar moulding 348, a blade moulding 352 and an extension spring350, all of which are coupled together to form a three pivotslider-crank mechanism, as shown in FIGS. 20a-20b and FIGS. 31 and 32.

The drive arm 2000 is formed of a trigger 24 and the trigger moulding344, wherein the trigger 24 is a finger gripping member for actuatingthe cutting mechanism and the trigger moulding 344 is a collar having a“C” shaped side profile and an aperture 364 through which the driveshaft 316 is threaded. The point which the trigger 24 and triggermoulding 344 meet provides a pivot point A about which the drive arm2000 is rotated. This first pivot point A is anchored to the casing 20,for example, by means of outward facing pins 358 that connect withcorresponding mouldings 356 integral to the clamshell mouldings 300,302.

The distal end of the drive arm 2000, that is, the end of the triggermoulding 344 is pivotally connected to the blade drive moulding 346 toform a second pivot point B. The blade drive moulding 346 is an “H”shaped frame having two parallel arms and a strut therebetween. As such,the parallel arms of the blade drive moulding 346 are pivotallyconnected at one end to the trigger moulding 344, for example, by meansof outward facing pins 366 and mating connectors 368. At the oppositeend, the parallel arms of the blade drive moulding 346 are alsopivotally connected to the blade collar moulding 348 to form a thirdpivot point C, for example, by means of outward facing pins 372 andmating connectors 370.

As shown in FIGS. 21 to 23, the blade collar moulding 348 is acylindrical or barrel shaped component having a chamber 2104 in whichthe blade moulding 352 sits, wherein the blade moulding 352 is acylindrical or barrel shaped component having a body 362 that fitsinside the chamber 2104 of the blade collar moulding 348. The blademoulding 352 further comprises a flange 360 having a diameter largerthan that of the chamber 2104 such that the flange 360 abuts the distallip 2200 of the blade collar moulding 348, as shown in FIG. 22.Consequently, the flange 360 ensures that the correct end of the blademoulding 352 is interested to the blade collar moulding 348.

The body 362 is provided with a small groove 2202 around itscircumference so as to provide a shoulder with which the distal lip 2200interlocks such that the blade moulding 352 and blade collar moulding348 are coupled via a snap-fit connection. The distal lip 2200 mateswith the groove 2202 so as to retain the blade moulding 352 within theblade collar moulding 348 whilst allowing the blade moulding 352 tofreely rotate within the chamber 2104. As such, the blade moulding 352and blade collar moulding 348 are free to rotate concentrically.

Once the blade collar moulding 348 and blade moulding 352 have beenassembled together, the blade 340 can be connected as illustrated byFIGS. 24a-24c . In this respect, the blade moulding 352 comprises a “T”shaped aperture 2300 which extends throughout its length, shaped as suchso as to receive both the blade 340 and the drive shaft 316, as shown byFIG. 23.

The proximal end of the blade 340 comprises a tab feature 2102 whichextends beyond the general profile of rest of the blade 340, that is, itdoes not lie in the same axial plane. As shown in FIG. 24c , the body362 further comprises a recess 2100 in which the tab 2100 is retained.To enable assembly, the proximal end of the blade 340 is cut away at afirst point opposite the tab 2102 in order to provide a bevelled edge2400, and is cut away a second point adjacent to the tab 2102 to providea recessed portion 2402. As such, the proximal end of the blade 340 hasan “L” shaped profile.

To assemble the blade 340 within the blade moulding 352 and blade collarmoulding 348 assembly, the blade 340 is presented to the “T” shapedaperture 2300 at an angle to the longitudinal axis of the instrument 1so that the tab 2102 and bevelled edge 2400 can be inserted to theinternal cavity 2404 of the blade moulding 352, as shown in FIGS. 24a-24 b. The blade 340 is then pulled down in line with the longitudinalaxis so as to push the tab 2102 into the recess 2100, as shown by FIG.24c . As such, the tab 2102 is effectively hooked on to the shoulder2406 of the blade moulding 352, thereby retaining the proximal end ofthe blade 340 within the internal cavity 2404.

The drive shaft 316 may then be threaded through the “T” shaped aperture2300, the blade 340 being received in the central track 342, asillustrated by FIGS. 22 and 23. As such, longitudinal movement of theblade collar moulding 348 and blade moulding 352 assembly along thedrive shaft 316 drives the blade 340 along the track 342.

To complete the blade trigger assembly, an extension spring 350 extendsbetween the blade collar moulding 348 and drive arm 2000, for example,by means of hooks 2002, 2004.

In use, the user pulls the trigger 24 back towards the casing 20, asshown by FIGS. 25b -25 c, so as to pivot the drive arm 2000 around thefirst pivot point A. In doing this, the second pivot point B is pushedforwards in the distal direction which cause the drive moulding 346 topush the blade collar moulding 348 and blade moulding 352 assembly alongthe drive shaft. The load exerted on the trigger 24 is thereforetransferred to the blade collar moulding 348 and blade moulding 352 viathe trigger moulding 344 and drive moulding 346. As the proximal end ofthe blade 340 is retained inside the blade moulding 352 as describedabove, the blade 340 slides along the central track 342 with the bladecollar moulding 348 and blade moulding 352 assembly. As the blademoulding 352 is rotationally isolated within blade collar moulding 348,the draft shaft 316 can also be rotated without interfering with theoperation of the cutting mechanism.

The functionality of the mechanism is optimised so as to provide goodmechanical advantage at the beginning of the blade 340 travel, when theuser's finger is extended and not as strong, and also at the end of theblade 340 travel, where there are more forces working against the blade340 travel such as the force of the spring 350, friction within thetrack 342 and the force required to penetrate thick tissue. As can beseen from FIG. 27, a constant force is applied to the trigger 24 by theuser. The mechanism converts this trigger force into a high initialblade 340 force, which decreases as the blade 340 is driven along thetrack 342, and increases again as the blade 340 reaches the jaws 14.Therefore, as the pivot point B moves from its retracted position to itsprotracted position as shown by FIGS. 28a -28 b, such that β>90°, thespeed at which the blade collar 348 and blade moulding 352 are drivenalong the drive shaft 316 accelerates, thus increasing the force of theblade 340. As such, the mechanism is able to drive the blade 340 withenough force to effectively cut the tissue clamped between the jaws 14without the user needing to exert any additional force on the trigger24.

Additionally, the cutting mechanism may be required to push the blade340 around a curved set of jaws 14, adding to the frictional forcesworking against the blade 340 travel. The frictional force is a productof the frictional coefficient of the blade 340 within the track 342, andthe force due to bending that the blade 340 exerts on the walls of thetrack 342.

To reduce this frictional force, the lateral flexibility of the blade'sdistal end may be graduated. Such graduated flexibility may be achieved,for example, by preferentially weakening the blade 340 such that it isable to bend along the track 342 whilst remaining rigid in the directionof the cutting force. Preferential weakening may be provided, forexample, by the provision of one or more apertures or slots 354 in thedistal end, as shown in FIG. 47a . Such apertures may be of constant orvarying size of shape, depending on the degree of flexibility required.For example, in FIG. 47b , two contiguous apertures 4702, 4704 havingdifferent sizes are provided, wherein the larger aperture 4702 providesa greater degree of flexibility than the smaller aperture 4704. Asanother example, in FIG. 47c , three apertures 4706, 4708, 4710 ofvarying size and shape are provided, the largest aperture 4706 being themost distal so as to provide more flexibility in this region.Preferential weakening may also be achieved by graduating the thicknessof the blade 340 such that the distal end of the blade 340 is bevelled4700, as shown in FIG. 47 d.

Alternatively, patterned laser cuts 4702 or chemical etches in thedistal end may be used to control the bending stiffness over a length ofthe blade 340, as shown in FIG. 47e , whereby the spacing between suchcuts may be constant or gradually increase from the distal to proximalend.

Preferably, the blade 340 is divided into at least three regions ofvarying flexibility. For example, a distal region, an intermediateregion and a proximal region, wherein the distal region has a greaterlateral flexibility than the intermediate region, and the intermediateregion has greater flexibility than the proximal region. For example,the distal region may be formed of a bevelled end 4700 to give thegreatest degree of flexibility, the intermediate region formed of anaperture 354 to provide a relatively lower amount of flexibility, andthe proximal region formed of a solid bar to give even less flexibility,as illustrated by FIG. 47a . In a further example shown by FIG. 47b ,the distal region includes a large aperture 4702 to give the greatestdegree of flexibility, the intermediate region includes a smalleraperture 4704 to provide decreased flexibility and the proximal regionis once again a solid bar having the lowest degree of flexibility. Assuch, the distal region, intermediate region and proximal region may beachieved using any suitable combination of the preferential weakeningdescribed above.

A further way of reducing the frictional force due to the curved trackis to add a low friction coating to at least one side of the distal endof the blade 340. For example, the blade may be coated, for exampleusing physical vapour deposition (PVD) or chemical vapour deposition(CVD) processes, with a low friction or non-stick material, such as aPTFE composite or other low friction polymer composite.

5. Drainage Apertures

Various further features and aspects relating to the structure of thedrive shaft 316 will now be described. As described above, the driveshaft 316 is an elongate bar having a “T” shaped cross-section, asillustrated by FIG. 10a . The drive shaft 316 comprises a slot or track342 along its length suitable for housing a further elongate member,such as the cutting blade 340 used in the cutting mechanism describedabove. In use, the cutting blade 340 is caused to slide along the lengthof the drive shaft 316 so as to drive the distal end of the cuttingblade 340 between the jaws 14 in order to cut tissue clampedtherebetween.

Over time, blood and tissue can start to build up within the distal endof the instrument 1, particularly down the length of the outer shaft 12and drive shaft 316. This build-up of blood and tissue can cause theblade 340 to stick within the drive shaft 316, thus reducing thefunctionality of the instrument 1, in particular, that of the cuttingmechanism. To combat this, portions of the distal end of the drive shaft318 are cut out in order to reduce the area of contact between the driveshaft 316 and the blade 340 and thereby reduce the surface area to whichblood and tissue can stick.

These cut out portions may be apertures such as the elongate windows1000, 1002 shown in FIGS. 10b -10 c, such that the distal end of thedrive shaft 316 comprises a base support with bifurcated side walls. Thecut out portions may also extend to the base of the drive shaft 316 suchthat the distal end comprises bifurcated side walls and an open bottom.In order to maximise the amount of drainage afforded by these apertures1000, 1002, the apertures are preferably more than 50% of the depth ofthe drive shaft 316.

As such, these apertures 1000, 1002 provide drainage passages betweenthe central track 342, and the exterior of the drive shaft 316.

6. Rotation Wheel and Switch

Various further features and aspects relating to the operation of thethumbwheel (also referred to herein as a rotation wheel) 28 will now bedescribed. The thumbwheel 28 is provided to allow the user to rotate theouter shaft 12 on which is mounted the end effector assembly 14.However, in order to reduce space, and hence produce a more compactinstrument, the inner volume 1300 of the thumbwheel 28 is also utilisedto provide movement space for the inner moulding 314, that forms part ofthe clamping mechanism described previously. With such an arrangement, amore compact mechanism can be obtained.

In more detail, the rotation wheel 28 (also referred to herein as athumbwheel), comprises a plastic cog-like wheel, having a plurality ofscallop portions 336 located around its external diameter. As such, thethumbwheel 28 takes the appearance of a cog, having the scalloped cutout portions arranged to receive a user's thumb, in an ergonomicfashion. In this respect, as shown in more detail in FIGS. 13a, 13b ,and in particular in FIG. 14a , the scallop portions are angled to theplane of rotation of the thumbwheel when in use, such that generally thethumbwheel or rotation wheel 28 is slightly frusto-conical in shape,being wider at a distal end from the user than it is at the proximal endtowards the user. The scallop portions 336 each extend from the distaledge of the thumbwheel to the proximal edge, and are curved or saddlelike in shape to receive a user's thumb, when in use. As shown in detailin FIG. 14a , the angling of the scallop portions 336 to give thefrusto-conical shape of the rotation wheel 28 generally matches theangle of the body of the instrument. In FIG. 14a the dot-dash linesillustrate the angling of the scalloping 336 around the edge of thewheel 28, which can be seen to be tangential to the angle of the outerwalls of the instrument at the point around the wheel, and in particularof the portion of the outer walls of the instrument immediately in frontof the wheel, in a distal direction. Such an arrangement where theangled scalloping of the outer rim of the rotation wheel matches theangling of the wall of the instrument around the wheel provides acomfortable and ergonomic design, which is easy to operate by thesurgeon.

In terms of the number of scallop portions 336 around the outer diameterof the wheel 28, as shown in one embodiment eight scallop portions areevenly distributed around the outer diameter of the wheel. In otherembodiments, fewer, or larger number of scallop portions may be used,for example as few as six or seven, or as many as nine or ten. If alarger wheel 28 was to be employed, then a greater number of scallopportions 336 may be included, and conversely if a smaller wheel isemployed then the number of portions may be fewer in number. In thisrespect, the actual size of each scallop portion 336 should typicallyremain the same, as the scallop portions have been ergonomically chosenso as to be able to receive a user's thumb comfortably.

Regarding the positioning of the thumbwheel 28 within the instrument, asshown in FIG. 2, the rotation or thumbwheel 28 is positioned verticallyoriented beneath the switch 26, and spaced from the thumbwheel in adirection orthogonal to a longitudinal axis defined for example by thelongitudinal direction of drive shaft 316. In particular, thehand-switch 26 lies directly on an axis orthogonal to such alongitudinal axis and which also passes through the thumbwheel 28.Moreover, as shown in FIGS. 14a and 14b , the switch 26 is relativelylarge in size, and extends from one side of the upper surface of theinstrument to the other, above the thumbwheel. The switch 26 is curvedin nature, generally to match the curved upper surface of the outer wallof the instrument, and has bumps, grooves, or other raised protrusionson the outer surface thereof, to aid with the user being able to gripthe switch in order to be able to press it, with his or her thumb. Thesurface area of the switch 26 is relatively large, being in excess of 3cm² or even 5 cm². This provides a large surface area, to allow forergonomic activation thereof by the user. The vertical orientation ofthe switch 26 directly above the thumbwheel 28 also allows for ergonomicactivation. As explained elsewhere, the switch 26 in use operates tocause an RF coagulation signal to be fed to the end effector, forcoagulation of any tissue located therein.

Concerning the ergonomics of the switch and thumbwheel, FIGS. 35a and35b are two respective photographs of different users with differentsize hands. As demonstrated, the switch 26, being of a relatively largesurface area is easy to operate by users with different hand sizes, atthe same time as operating clamping handle 22 (and blade trigger 24, ifdesired).

Returning to FIG. 12, as described previously the thumbwheel 28 has aninternal cavity 1300 within which is received in use the inner moulding314. As described previously, the inner moulding 314 comprises an innermoulding chamber 610 and has a T-shaped cut through portion 1208therein, into which the drive shaft 316 is received therethrough, andfastened therein, as described previously. The inner moulding 314 snapfits into the interior cavity of the wheel 28, and flanges 1206, asshown in FIG. 12 and FIGS. 29a and 29b are provided around the outeredge of the cylindrical interior cavity 1300 of the thumbwheel 28, tohold the inner moulding 314 in place within the cavity, once it has beeninserted therein. The interior cavity 1300 of the thumbwheel 28 is alsoprovided with interlocking members 1200, which interact withcorresponding interlocking members 1202 provided around the outercircumference of the inner cylindrical moulding 314. The respectiveinterlocking members 1200 and 1202 comprise respective raised stepportions that fit together side by side circumferentially around theinner surface of the cavity 1300 when the thumbwheel 28 and the innercylindrical moulding 314 are in the correct rotational alignment withrespect to each other. The respective interlocking members 1200 and 1202are provided so that in use the inner cylindrical moulding 314 may slidefrom side to side within the interior cavity of the wheel 28, but maynot rotate within the wheel 28. Instead, the interacting interlockingmembers 1202 and 1200 act so that the inner moulding 314 rotates withthe rotation wheel 28, as it is rotated. In this way, any rotationaltorque applied by the user 28 to the rotation wheel 28 is transferred tothe inner moulding 314, and then to the drive shaft 316, in order torotate the driveshaft, carrying the end effector. FIGS. 29a and 29b showthe inner moulding 314 inserted into the interior cavity of thethumbwheel 28, and illustrate how the inner moulding 314 may slideaxially within the inner cavity 1300 of the wheel 28.

FIGS. 13a and 13b also show in more detail how the inner moulding 314 isable to move within the inner cavity 1300 of the wheel 28. As describedabove, the drive shaft 316 passes through the T-shaped aperture 1208 inthe inner moulding 314, and is secured therein via snap fit protrudingcatch or latch members 602, provided on the end of the drive shaft. Thatis, latch or catch members 602 are in the form of sprung metal tabs thatare able to pass through the T-shaped aperture 1208 within the innermoulding 314, and are then received in an inner moulding second channelpart 606 forming a cavity which allows the spring tabs to spring apart,thus securing the drive shaft within the inner moulding. The innermoulding 314 is then pushed into the inner cavity of the thumbwheel1208, and is held in place by the snap fit tabs 1206, as describedabove. The inner moulding may move axially within the inner cavity 1300so as to abut against the inner surface of the distal wall of the wheel28, as shown in FIG. 13a , or, at its opposite end of travel, to abutagainst the tabs 1206 at the distal edge of the wheel. Thus, the innermoulding 314 is provided with a degree of axial sliding movement withinthe cavity of the thumbwheel 28, which is required as part of themechanism to control the force applied by the user to material containedwithin the jaws, as described above.

The snap fit nature of the inner moulding 314 into the inner cavity ofthe thumbwheel 28 hugely improves the assembly of the device, and makesthe device significantly easier, and hence cheaper to assemble.Likewise, in order to position the thumbwheel within the casing, asshown in FIG. 33, the outer distal wall 1310 of the thumbwheel 28 isconcentric with and aligned to an internal supporting wall 1320,provided as a projection from the casing of the device. This also allowsfor easy and accurate assembly and positioning of the wheel 28 withinthe casing.

7. Rotational Control of Drive Shaft

As explained above, shaft 12 having end effector 14 thereon is rotatableto allow the end effector to be moved into desired rotational positionsfor the cutting and coagulation of tissue. However, in order that thewiring connections to the end effector are not placed under excessstrain from the shaft being rotated in one direction too far such thatthe wiring becomes wound up, twisted, or placed under excessive strain,a mechanism to control the rotation of the shaft 12 is required, inparticular to limit the amount of rotation, and thereby prevent excessstrain on the wiring. In addition, providing positive control of therotation of the shaft 12 improves the ergonomic experience of theinstrument when in use, and enhances the user perception of quality.

In order to provide rotational control of the shaft in one embodiment anarrangement as shown in FIGS. 15a and 15b , and FIGS. 16a to 16d isemployed. With reference to FIG. 15, here thumbwheel 28 having scallopportions 36 is provided on its proximal surface (i.e. rearward face,facing the user) with a ring 1506 that projects slightly from theproximal surface arranged concentric with the axis of the wheel 28. Thering 1506 rests in use on guide stop features 1502 and 1504, beingprojections from the inner surface of the outer casing, that project upto make contact with the outer circumference of the ring 1506. Stopfeature 1502 is smaller than stop feature 1504 due to their positioningon the casing with respect to the axis of the ring, but both stopfeatures 1502 and 1504 have angled upper guide faces 1510 and 1512 (seeFIG. 15a ) respectively, that contact with the outer circumferentialsurface of ring 1506 forming part of the thumbwheel, and help to supportand guide the thumbwheel in its rotation.

In addition, to providing a guiding function, stop features 1502 and1504 also act as stop members to prevent the rotation of the thumbwheelpast the angular position of the stop features. In this respect, thering 1506 is provided with a rectangular stop projection 1500 radiallyextending therefrom. As the thumbwheel 28 is rotated the stop projection1500 abuts against respective stop faces 1514 and 1516 of the stopfeatures 1502 and 1504. The stop faces are angled to be parallel to therectangular stop projection 1500 when the stop position is angularlypositioned so as to be abutted thereagainst.

The stop features 1502 and 1504 arranged as described above arepositioned, and are of such a length so as to provide a known amount ofrotation of the wheel 28 from stop feature 1500 to stop feature 1502. Inthe presently described arrangement shown in FIG. 15a and FIG. 15b thestop features 1502 and 1504 are positioned on the casing with a spacingtherebetween so as to allow the thumbwheel to rotate 270° from stop tostop. The amount of rotation can be varied slightly by increasing ordecreasing the distance between the stop features, with the stopfeatures being adapted in length and angle of the guide and stop facesaccordingly so as to still meet the wheel and the stop featuressubstantially normally, respectively. For example, the stop features maybe positioned and shaped to provide angular rotation of the wheel ofbetween 250° and 300°.

The above describes the rotational control that is applied to thethumbwheel (and then to the shaft via the thumbwheel). FIGS. 16a to 16dshow a further rotational control mechanism that is applied to the shaftat the opposite end of the shaft, using shaft moulding 320. Here, shaftmoulding 320 is provided with rectangular stop member 1600 projectingtherefrom. The inner surface of the outer casing is further providedwith respective moulded stop features 1602, and 1604, shown in the formof stepped feature providing respective stop surfaces that present tothe rectangular stop member 1600 respective parallel stop surfaces atrespective angular positions of the shaft moulding 320. In the exampleshown, the moulded stop features are positioned on the casing andpresent respective stop surfaces to the stop member 1600 to permit arotation of 270° of the shaft 12 carrying the end effector from stop tostop. In other embodiments, the moulded stop features 1602 and 1604 maybe positioned to present stop surfaces to the stop member 1600 at otherrotational angular positions of the moulding 320, to provide a greateror lesser amount of rotation, for example from 180° to 360°, or morepreferably from 250° to 300°, or most preferably 270°.

The respective rotation control mechanisms provided in the thumbwheel 28and the shaft moulding 320 may be provided independently from each otheri.e. they need not both be provided in any particular embodiment, butonly one or the other may be provided to provide for rotational controlof the shaft. However, it is advantageous in terms of operation and theperception of quality of the device for both the rotation controlmechanisms to be provided in the same device, and to be aligned suchthat they provide for stopping of rotation at the same respectivepoints, in either rotational direction. Such an arrangement means thatthe rotation of the shaft is stopped independently at both ends of thehandle portion 10, and it becomes very difficult for a user to forcefurther undesirable rotation of the shaft past the allowed limitsrepresented by the stops.

An alternative rotational control mechanism is shown in FIGS. 36 and 37.FIG. 36 illustrates again the shaft moulding 320, but here the mouldingis provided with ring 3220 on which is mounted a primary rectangularstop member 3202 projecting radially therefrom, and secondary positionmarker members 3204, 3206, and 3208, positioned around the ringsubstantially equiangularly, preferably at orthogonal positions. Thesecondary position marker members 3204, 3206, and 3208 constitute smallraised projections that are not large enough to about against stop faces3212 and 3214.

Stop faces 3212 and 3214 are provided as integral mouldings with theouter casing, and are positioned here so as to permit the shaft moulding320 to be rotated by 180°. In this respect, the stop member 320 abutsagainst the stop faces 3212 and 3214 at the ends of the rotation range,to prevent further rotation of the shaft moulding. Hence, as shown inFIGS. 36 a) to 36 c), the shaft moulding 320 carrying the shaft 12 mayrotate through 180°, to allow the end effector to be positionedrotationally as desired.

Also provided is a sprung projection 3216, comprising a plasticprojection of substantially triangular cross-section that projectsupwardly from the moulding forming stop face 3214, such that its tipcontacts the outer circumferential surface of ring 3220. The secondaryposition markers in the form of the small raised projections pressagainst the tip of the sprung projection as the shaft moulding 320rotates, causing the tip of the sprung projection to move out of itsrest position to allow the respective projection to move past the tip.The effect of this operation is to provide some user feedback in thatthe user must apply more force to rotate the mechanism past therotational positions where the raised projections contact the tip of thesprung projection, because sufficient force must be provided to causethe tip of the sprung projection to deflect, to allow the projection tomove past the tip. The result of this is that the user feels an increaseof force required to rotate the shaft past the rotational positions ofthe raised projections, and hence intuitively the user is provided withan indication of the rotational position of the shaft, and hence the endeffector. Such a haptic feedback mechanism thus allows for user friendlyand easy operation of the device.

FIG. 37 illustrates the corresponding thumbwheel 28 for the mechanism ofFIG. 36. Here, the thumbwheel is also provided with respective smallstops 3222, arranged orthogonally at 90° intervals around thethumbwheel. A similar mechanism to the sprung projection 3216 may beprovided, projecting from the casing, to provide similar haptic feedbackas in the case of the shaft moulding 320. In such an arrangement, hapticfeedback as to the rotational position of the shaft is provided fromboth ends of the handle, and hence the user perception of the device isimproved.

8. Wiring

Various further features and aspects relating to the wiring within thehandle 2 will now be described. As described above, the switch button 26is provided for activating and de-activating the RF signal for operatingthe electrodes in the end effector assembly 14 via some appropriatecircuitry, for example, two ingress-protected switches on a smallprinted circuit board (PCB) 338. As shown in FIG. 17, the PCB 338 isconnected to a connection cord 1700 for receiving the RF output from agenerator (not shown) and electrical wiring 1702, 1704 for supplying theRF current to the electrodes in the jaws 14, for example, one wire forthe active electrode and one for the return electrode.

In assembly, the wiring 1702, 1704 from the electrodes is fed down theouter shaft 12 alongside the drive shaft 316 and up to the shaftmoulding 320, as illustrated by FIG. 17. As shown in FIG. 9b , the shaftmoulding 320 is a cylindrical or barrel shaped component having anopening 912 at the distal end to receive the outer shaft 12. The outershaft 12 is attached to the shaft moulding 320, for example, by snap-fittabs 900 that cooperate with corresponding notches 902 within the shaftmoulding 320. Consequently, if the shaft moulding 320 rotates, the outershaft 12 rotates with it. The shaft moulding 320 further comprises afurther aperture 914 at the proximal end, the aperture 914 having a “T”shape so as to receive the drive shaft 316, wherein the drive shaft 316extends through the internal cavity 1802 of the shaft moulding 320 anddown the length of the outer shaft 12. As such, the drive shaft 316 isable to slide within the shaft moulding 320 and outer shaft 12, but anyrotational movement of the drive shaft 316 is transferred to the shaftmoulding 320 and subsequently the outer shaft 12.

As shown in FIG. 18a , the electrode wires 1702, 1704 are fed out of theinternal cavity 1802 through an opening 1800 in the wall of the shaftmoulding 320 before being wrapped over and around the body 1804 of theshaft moulding 320. Wrapping the wires 1702, 1704 around the shaftmoulding 320 in this way keeps the wires 1702, 1704 in a compactarrangement so as prevent the wires 1702, 1704 from getting in the waywhen assembling the rest of the instrument 1. Furthermore, wrapping thewires 1702, 1704 around the shaft moulding 320 means that as the shaftmoulding 320 rotates with the drive shaft 316, the wires 1702, 1704un-wind and re-wind with said rotation without pulling on the wires1702, 1704 and causing them to short. Specifically, wrapping the wires1702, 1704 in this particular way allows for up to 270° of rotation, asdescribed with reference to FIGS. 15a-b and 16a -d.

The electrical wiring 1702, 1704 is then passed along the top of thecasing 20. In this respect, one of the clamshell mouldings 300 isprovided with two pockets 1900, 1902 located in series for housing thewire contacts 1904, 1906 that connect the active and return wires 1702,1704 to the wiring 1908, 1910 of the ingress-protected switches 338.Consequently, all of the electrical wires 1702, 1704, 1908, 1910 arerouted in and around the pockets 1900, 1902 so that only one contact1904, 1906 is housed in each pocket 1900, 1902. The routing of the wiresmay be aided by guide portions 1912, 1914, 1916 which direct one set ofthe wires 1702, 1910 around the outside of the pockets 1900, 1902.Within each pocket the respective active wire 1702 is longitudinallyaligned with wire 1908, and return wire 1704 is longitudinally alignedwith wire 1910.

As a result, the two wire contacts 1904, 1906 are longitudinallyseparated such that only one contact can pass through each pocket 1900,1902, thereby providing a physical barrier between each contact 1904,1906 and any wiring. This prevents the risk of insulation damage to anyof the wiring caused by the contacts 1904, 1906 themselves.

The wires 1702, 1704, 1908, 1708 all enter their respective pockets1900, 1902 through small openings 1918, 1920, 1922, 1924 in the walls ofthe pockets.

Preferably, the dimensions of the apertures 1918, 1920, 1922, 1924 aresuch that only one electrical wire can fit through. The oppositeclamshell moulding 302 also comprise corresponding rib features (notshown) to retain the contacts 1904, 1906 within the pockets 1900, 1902,so as to form a substantially sealed housing. This is important forminimising the permeability of the pockets 1900, 19200 in order toprotect the contacts 1904, 1906 from any fluid that may make its waydown the outer shaft 12 and into the casing 20, thus causing thecontacts 1904, 1906 to short circuit.

9. End-Effector Assemblies

Example end-effector assemblies that may be used with the apparatus willnow be described. The examples to be described are given forcompleteness only, and it should be understood that other designs ofend-effector may also be used with the instrument, provided they areable to be driven by drive shaft 316. That is, embodiments of theinvention are not limited to the specific end-effectors describedherein, and other designs of end-effector may also be used.

FIGS. 38 to 44 show example instruments where the electricallyconductive stop members are disposed on one or both of the sealingelectrodes. Referring to FIG. 38, an end effector shown generally at3801 comprises an upper jaw 3802 pivotably connected to a lower jaw 3803about a pivot 3804. Flanges 3805 are present at the proximal end ofupper jaw 3802, while flanges 3806 are present at the proximal end oflower jaw 3803. The flanges 3805 & 3806 each have slots 3807 throughwhich a drive pin 8 extends, such that proximal and distal movement ofthe drive pin 3808 (by means of a drive mechanism (not shown) causes thejaws 3802 & 3803 to pivot between open and closed positions.

A metallic shim 3809 is present on the inward face of upper jaw 3802,while a metallic shim 3810 is present on the inward face of lower jaw3803. When the jaws 3802 & 3803 pivot into their closed position, themetallic shims 3809 & 3810 come into close proximity one with the other,in order to grasp tissue (not shown) therebetween.

The upper shim 3809 has a generally planar surface, with the exceptionof a longitudinal groove (not visible in FIG. 38) running the lengththereof. The lower shim 3810 has a corresponding groove 3811, thegrooves in the shims 3809 & 3810 accommodating the longitudinal movementof a cutting blade (not shown). The lower shim 3810 is also providedwith a plurality of metallic stop members 3812, disposed along thelength of the shim and situated on either side of the groove 3811. Thestop members 3812 will now be described in more detail, with referenceto FIGS. 39 & 40.

Each metallic stop member 3812 is constituted by the upper dome of astop element 3813, which is enclosed in an insulating member 3814 suchthat it encapsulates the stop element isolating it from the remainder ofthe shim 3810. Each insulating member 3814 and stop element 3813 ispositioned in a corresponding aperture 3815 present within the shim3810, such that the upper portion of the insulating member forms aninsulating ring 3816 around each stop member 3812.

When the jaws 3802 & 3803 are moved to their closed position (as shownin FIG. 40), the stop members 3812 contact the upper shim 3809maintaining a separation between the upper and lower shims of between 20μm and about 350 μm (0.00079 inches to about 0.014 inches). In use, acoagulating electrosurgical voltage is supplied between the shims 3809 &3810, and the separation of the shims ensures effective sealing oftissue grasped between the jaw members 3802 & 3803. In the meantime,electrical shorting between the shims is prevented, as the stop members3812 are electrically isolated such they do not carry the same electricpotential as the remainder of the shim 3810. The metallic stop members3812 are rigid, allowing for a consistent separation of the shimsurfaces, while it is feasible that the electric potential of the stopelements 3813 can be monitored in order to detect when they contact theupper shim 3809 to give an indication of the closure of the jaws.

FIGS. 41 to 43 show an alternative arrangement in which the metallicstop members 3812 are mounted directly on the lower shim 3810, withoutthe provision of the insulating members surrounding the stop members. Inthis arrangement, insulating members 3817 are provided on the upper shim3809, in corresponding relationship to each of the stop members. In thisway, when the jaws 3802 & 3803 are closed, the insulating members 3817ensure that there is no electrical shorting between the upper shim 3809and the lower shim 3810. The metallic stop members 3812 ensure that theappropriate separation of the jaw members is maintained during theapplication of electrosurgical energy in order to seal tissue graspedbetween the jaws.

Finally, FIG. 44 shows a further alternative, in which the metallic stopmembers 3812 are once again mounted directly on the lower shim 3810. Inthis arrangement, a metallic anvil 3818 is located opposite each of thestop members, each metallic anvil 3818 being surrounded by an insulatingmember 3819 in order to isolate it from the remainder of the upper shim3809. When the jaws are closed, metal-to-metal contact takes placebetween the stop members 3812 and the metallic anvils 3818, with theisolation of the anvils ensuring that electrical shorting between theshims 3809 & 3810 is once again avoided. Once again, the electricpotential of each of the metallic anvils can be monitored in order todetect when they assume the potential of the lower shim, indicatingclosure of the jaws.

10. Electro-Surgical System

Referring now to FIG. 45, the instrument 1 in use is intended forconnection to an electrosurgical generator 4500 having a controllableradiofrequency (RF) source therein (not shown) that in use produces anRF coagulation signal that coagulates or seals tissue when appliedthereto via the electrodes of the end-effector of the instrument 1.Electrosurgical generator 4500 includes control input switches 4504 and4502, to respectively allow the generator to be turned on and off, andto allow the power of the RF coagulation signal fed to the instrument 1to be controlled. In these respects, the electrosurgical generator 4500is conventional.

The instrument 1 is connected in use to generator 4500 by control andpower line 4506, which contains separate electrical lines to allow an RFsignal to be fed to the end-effector of the instrument 1 via theinternal wiring described previously, and also to allow a control signalto be received from the switch 26 of the instrument 1, to command theelectrosurgical generator to output an RF coagulation signal to theinstrument 1. In use the surgeon activates the generator via on-offswitch 4504, and selects the coagulation or sealing signal strength tobe generated by the internal RF source using buttons 4502. During asurgical procedure with the instrument when a sealing or coagulation RFsignal is required at the end-effector, the surgeon controls thegenerator to produce such a signal by pressing the switch 26 on theinstrument, the generated RF signal then being passed via the electricallines 4506 to the end-effector. That is, pressing of the switch 26 inuse causes an RF coagulation or sealing signal to be supplied to theappropriate electrodes contained within the end-effector.

11. Summary

In view of all of the above, therefore, embodiments of the inventionprovide an advanced electrosurgical forceps instrument which allows foreasy and ergonomic one-handed operation by the user, provides rotationalflexibility of the end-effector, controls the force that is applied bythe end-effector to the tissue being grasped so as to prevent excessiveforce being applied, and allows for a convenient mechanical cut of thegrasped tissue whilst at the same time providing for electrosurgicalcoagulation or sealing of the tissue. Moreover, the instrument has beenfurther designed so as to be simple and low-cost to construct, whilstproviding a compact instrument through efficient use of the spaceavailable within the respective internal activation mechanisms.

Various further modifications to the above described embodiments,whether by way of addition, deletion or substitution, will be apparentto the skilled person to provide additional embodiments, any and all ofwhich are intended to be encompassed by the appended claims.

1. A surgical instrument including a handle, an elongate shaft extendingfrom the handle and defining a longitudinal axis for the instrument, ablade assembly located within the elongate shaft, the blade assemblyincluding a cutting blade at its distal end, the blade assembly beingconnected at its proximal end to a component within the handle, atrigger mechanism located on the handle and movable between a firstposition and a second position, movement of the trigger mechanism fromits first position to its second position causing the movement of thecomponent within the handle and hence the longitudinal movement of thecutting blade, wherein the component comprises a casing having a chambertherein, the chamber being sized to receive the proximal end of theblade assembly, the casing including at least one shoulder so as toprovide an opening to the chamber, the opening being of a smaller widththan that of the chamber, the proximal end of the blade assembly beingprofiled such that it offers a first width when the blade assembly ispresented to the opening at a predetermined angle to the longitudinalaxis of the instrument, the first width being less than that of theopening, the profile of the proximal end of the blade assembly beingsuch that it offers a second width when the blade assembly is presentedto the opening aligned with the longitudinal axis of the instrument, thesecond width being greater than that of the opening, such that theproximal end of the blade assembly can be inserted into the chamber whenthe blade assembly is presented to the opening at the predeterminedangle to the longitudinal axis of the instrument, but the proximal endof the blade assembly is constrained within the chamber when the bladeassembly is moved along the longitudinal axis of the instrument.
 2. Asurgical instrument according to claim 1, wherein the proximal end ofthe blade assembly is in the form of a bar, having a thicknesssubstantially less than either its width or its length.
 3. A surgicalinstrument according to claim 2, wherein the proximal end of the bladeassembly includes a tab at its proximal extremity, the tab extending inone direction beyond the profile of the remainder of the proximal end ofthe blade assembly.
 4. A surgical instrument according to claim 3,wherein the proximal end of the blade assembly includes a recessedportion adjacent the tab.
 5. A surgical instrument according to claim 4,wherein the proximal end of the blade assembly includes a cut-awayopposite the tab.
 6. A surgical instrument according to claim 5, whereinthe cut-away comprises a beveled edge to the blade assembly.
 7. Asurgical instrument according to claim 5, wherein the first width isconstituted by the distance between the recessed portion and thecut-away.
 8. A surgical instrument according to claim 5, wherein thesecond width is constituted by the distance between the tab and theblade assembly adjacent the cut-away.
 9. A surgical instrument accordingto claim 4, wherein the recessed portion is curved so as to guide thetab into the chamber as the blade assembly is rotated from thepredetermined angle towards the longitudinal axis.
 10. A surgicalinstrument according to claim 9, wherein the shoulder is curved to as tomatch the profile of the recessed portion.
 11. A surgical instrumentaccording to claim 1, wherein the casing comprises a two-piece assembly,a first piece defining the chamber and a second piece defining theshoulder.
 12. A surgical instrument according to claim 11, wherein thesecond piece is rotatably connected to the first piece.
 13. A surgicalinstrument according to claim 1, and further comprising an end effectorpositioned at the distal end of the elongate shaft, the blade assemblyhaving the cutting blade at its distal end in the region of theend-effector.
 14. A surgical instrument according to claim 13, whereinthe end effector is an electro-surgical end-effector comprising one ormore electrodes.
 15. A surgical instrument comprising: a handle, anelongate shaft extending from the handle and defining a longitudinalaxis for the instrument, a blade assembly located within the elongateshaft, a trigger mechanism located on the handle and movable between afirst position and a second position, the trigger mechanism having acomponent connected to the proximal end of the blade assembly, thearrangement of the trigger mechanism and the component being such thatmovement of the trigger mechanism from its first position to its secondposition causes longitudinal movement of the blade assembly, wherein thecomponent comprises an internal cavity of a first shape profile and theproximal end of the blade assembly is of a second shape profile, thefirst shape profile and second shape profile being selected so as topermit the proximal end of the blade to be inserted into the internalcavity at an angle to the longitudinal axis, and to secure the proximalend of the blade within the internal cavity when the blade issubsequently rotated towards the longitudinal axis.
 16. A surgicalinstrument according to claim 15, wherein the blade is rotated to restparallel to the longitudinal axis to lock the proximal end of the bladewithin the component.
 17. A surgical instrument according to claim 16,wherein the internal cavity has a substantially L-shaped profile, andthe proximal end of the blade assembly has a corresponding substantiallyL-shaped profile but with material removed from inner and outer surfacesof the corner of the L as to reduce the width of the L-shaped profile atthe corner thereof.
 18. A method of assembling a surgical instrumenthaving a handle, an elongate shaft extending from the handle anddefining a longitudinal axis for the instrument, a blade assemblylocated within the elongate shaft, and a trigger mechanism located onthe handle and movable between a first position and a second position,the trigger mechanism having a component connected to the proximal endof the blade assembly to receive and retain the proximal end, the methodcomprising: presenting the proximal end of the blade assembly to thecomponent at an angle to the longitudinal axis of the instrument;receiving the proximal end of the blade assembly within an internalcavity of the component at the presented angle; and rotating the bladeassembly towards the longitudinal axis to secure the proximal end of theblade assembly within the internal cavity; wherein the proximal end ofthe blade assembly and the internal cavity of the component are ofrespective co-operating shapes so as to permit the receiving of theproximal end within the internal cavity at the presented angle and tothen secure the proximal end within the cavity at after the rotation ofthe blade assembly.
 19. A method according to claim 18, wherein theinternal cavity has a substantially L-shaped profile, and the proximalend of the blade assembly has a corresponding substantially L-shapedprofile but with material removed from inner and outer surfaces of thecorner of the L as to reduce the width of the L-shaped profile at thecorner thereof.